This invention relates to a centrifugal separator of the type which can be used to extract heavy metals such as gold from a slurry containing the metal mixed with other materials.
My issued U.S. Pat. No. 4,608,040 and disclose a device of this type which comprises a centrifuge bowl having a base and a peripheral wall surrounding an axis passing through the base and generally upstanding from the base to an open mouth, a plurality of axially spaced inwardly projecting rings mounted on an inner surface of the peripheral wall and a plurality of openings extending through the peripheral wall from the outer surface to the inner surface thereof, the openings being arranged between each ring and the next adjacent ring and in spaced relation around the peripheral wall, means mounting the bowl for rotation about the axis, means for feeding the materials into the bowl so that during rotation of the bowl they flow over the peripheral wall for discharge from the open mouth and means for applying fluid to the outer surface of the bowl so as to pass through the openings and fluidize the materials between the rings.
This device has been found to operate very satisfactorily and in a considerably improved manner relative to prior art devices Such prior art devices are shown for example in my Canadian Patent No. 111809 and in old Australian Patents 22055/35 and 17487/34 (MacNicol).
However there remains opportunity for further improvement in operational reliability of the device and in construction of the device which enables improved wear characteristics.
The present invention provides a number of improvements over my above described device which can improve wear resistance and operational reliability.
In one particular problem, the restriction to flow of the outer fluid through the holes into the bowl can cause solids in the form of silt to collect in the area surrounding the bowl, eventually leading to a loss of the required fluid flow.
According to a first aspect of the invention, therefore, there is provided apparatus for centrifugally separating intermixed materials of different specific gravities comprising a centrifuge bowl having a base and a peripheral wall surrounding an axis passing through the base and generally upstanding from the base to an open mouth, axially spaced inwardly projecting peripherally extending members defined on an inner surface of the peripheral wall so as to provide a peripherally extending recess between each member and the next adjacent member, and a plurality of openings extending through the peripheral wall from an outer surface to the inner surface thereof, the openings being arranged in the recess between each member and the next adjacent member and in spaced relation around the peripheral wall, means mounting the bowl for rotation about the axis, means for feeding materials into the bowl such that during rotation of the bowl they flow over the peripheral wall for discharge from the open mouth, ah outer bowl member surrounding the outer surface of the bowl, means for supplying fluid under pressure between the outer surface of the bowl and the outer bowl member so as to pass through the openings and fluidize the materials in the recesses, said outer bowl member comprising a sleeve member coaxially surrounding said peripheral wall, an outer bowl base and annular cover portion between said sleeve member and said bowl adjacent said open mouth said sleeve member being tapered to define a diameter thereof which increases from one and of the sleeve member adjacent the base to an opposed end of the sleeve member adjacent the open mouth of the bowl, and means defining a plurality of openings in said outer bowl member adjacent said opposed end of the sleeve member to allow escape of solid materials in said fluid.
In a further particular problem, the bowl can include a duct through the base through which the collected material is discharged after rotation of the bowl is halted. This duct is normally plugged during rotation However the plug in many cases can become disengaged during processing thus causing the fed materials to be ejected from the machine into an area reserved for collected concentrate. It is one object of the invention to provide an improved plugging arrangement for the bowl to avoid ejection of the plug.
According to a second aspect of the invention there is provided apparatus for centrifugally separating intermixed materials of different specific gravities comprising a centrifuge bowl having a base and a peripheral wall surrounding an axis passing through the base and generally upstanding from the base to an open mouth, axially spaced inwardly projecting peripherally extending members defined on an inner surface of the peripheral wall so as to provide a peripherally extending recess between each member and the next adjacent member, and a plurality of openings extending through the peripheral wall from an outer surface to the inner surface thereof, the openings being arranged in the recess between each member and the next adjacent member and in spaced relation around the peripheral wall, means mounting the bowl for rotation about the axis, means for feeding materials into the bowl such that during rotation of the bowl they flow over the peripheral wall for discharge from the open mouth, means for applying fluid to the outer surface of the bowl so as to pass through the openings and fluidize the materials in the recesses, a discharge duct mounted in said bowl through the base thereof, a removable plug member for closing the duct during rotation of the bowl, and latch means movable from a release position in which the plug member can be removed to a latching position for latching the plug member in a position thereof closing said duct, the latch means being movable to said latching position in response to centrifugal force generated by rotation of the bowl.
In a further problem, the high velocity and abrasiveness of liquid materials ejected from the bowl will cause rapid wear of the metal guide surfaces surrounding the bowl. While the above patents have proposed urethane liners to be attached to the metal surfaces the attachment techniques have not yet been satisfactory. It is one object of the invention therefore to provide an improved liner arrangement for the metal guide surfaces surrounding the bowl.
According to a third aspect of the invention there is provided apparatus for centrifugally separating intermixed materials of different specific gravities comprising a centrifuge bowl having a base and a peripheral wall surrounding an axis passing through the base and generally upstanding from the base to an open mouth, axially spaced inwardly projecting peripherally extending members defined on an inner surface of the peripheral wall so as to provide a peripherally extending recess between each member and the next adjacent member, means mounting the bowl for rotation about the axis, means for feeding materials into the bowl such that during rotation of the bowl they flow over the peripheral wall for discharge from the open mouth, a housing surrounding the open mouth for collecting and confining the material discharged therefrom, said housing defining an annular channel having an upper wall facing said open mouth and a peripheral wall surrounding said bowl which directs the material to an outlet duct and a wear resistant liner arrangement for said channel formed from a wear resistant plastics material, said liner arrangement including a cast annular ring attached to said upper wall at said peripheral wall and a cast cylindrical sleeve attached to an inner surface of said peripheral wall at said upper wall.
With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the best mode known to the applicant and of the preferred typical embodiment of the principles of the present invention, in which: